A Golgi study on the accessory olfactory bulb in the snake, Elaphe quadrivirgata

The intrinsic organization of the accessory olfactory bulb (AOB) in the snake was studied using the rapid Golgi method. A distinct laminar organization was observed in the snake AOB. Beginning with the most superficial surface, the following layers were distinguished: the layer of the vomeronasal fibers, the olfactory glomeruli, the mitral cells, the deep fiber plexus, the granule cells and the ependymal cells. While the general organizational pattern of the snake AOB resembles that of the main olfactory bulb (MOB) and the AOB reported in various vertebrate species, the present study shows that: (1) the external and internal plexiform layers cannot be identified as independent layers and are considered to be included in the mitral cell layer; (2) the afferent and efferent paths, which are disseminated in the granule cell layer in the mammalian MOB, accumulate external to the granule cell layer to form the layer of the deep fiber plexus: and (3) as a result of accumulation of the afferent and efferent paths in the layer of the deep fiber plexus, the granule cell layer is very fiber-sparse. These structural patterns are quite similar to those of the snake MOB.